Postoperative delirium in the elderly is associated with enormous personal, social, and economic burdens. The role of sedative medications as iatrogenic risk factors for delirium has been described in surgical and ICU patients. However, the role of intraoperative sedation as an iatrogenic risk factor for delirium is controversial. In the proposed study we build on our preliminary randomized trial which suggested that the rate of postoperative delirium might be cut by as much as half if sedation is limited during spinal anesthesia. This proposal is further motivated by early follow-up data from the preliminary RCT which suggested that limiting sedation during spinal anesthesia is associated with a decrease in 1-year mortality. We hypothesize that limiting level of sedation in elderly patients undergoing spinal anesthesia for hip fracture repair will reduce the incidence of postoperative delirium. We further hypothesize that limited sedation during spinal anesthesia will be associated with a decrease in 1-year mortality. These hypotheses will be tested in a randomized, controlled, clinical trial. Specific Aim 1 tests the hypothesis that limiting level of sedation will lead to a lower rate of postoperative delirium. Patients undergoing spinal anesthesia with propofol sedation will be randomized to one of two levels of intraoperative sedation: light sedation or heavy sedation. Level of sedation will be determined using the observer assessment of alertness/sedation scale score. Both groups will be assessed for postoperative delirium as defined by DSM-IV criteria, during their in-hospital stay and at 1-month follow-up, using the Confusion Assessment Method and delirium rating scale. Rates of postoperative delirium will be compared between groups. Specific Aim 2 tests the hypothesis that limiting level of sedation will lead to a lower 1-year mortality. Patients randomized to heavy or light levels of sedation will be compared by 1-year mortality and time to death over the 12 months after their operation. The method described in this proposal represents a new way of managing regional anesthesia in geriatric anesthesia practice. If the findings of the preliminary randomized controlled trial are confirmed in the proposed trial, this new method of regional anesthesia is likely to be adopted widely to reduce rates of postoperative delirium in this patient population. Public Health Relevance: Postoperative delirium is a common problem in the elderly with significant social and financial ramifications. In the proposed study we build on our preliminary randomized trial which demonstrates that the rate of postoperative delirium might be cut by as much as half if sedation is limited during spinal anesthesia. If the findings are confirmed in the proposed trial, this new method of managing intraoperative sedation during regional anesthesia is likely to be adopted widely to reduce rates of postoperative delirium in geriatric anesthesia practice.